Rhesus monkeys allowed to eat as much as they like had a 2.9 fold increased risk of disease and a three times increased risk of death

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Monkeys, Caloric restriction

A 25 year study of diet and ageing in monkeys has revealed a ‘significant’ reduction in mortality and age-related diseases among those with calorie restricted diets.

The research, published in Nature Communications, is one of two ongoing, long-term studies to examine the effects of a reduced-calorie diet on non-human primates.

Led by professor Richard Weindruch and his colleagues at the University of Wisconsin-Madison, the team reported that monkeys allowed to eat as much as they like had a 2.9 fold increased risk of disease and a three times increased risk of death when compared to those consuming a diet with 30% less calories.

"We think our study is important because it means the biology we have seen in lower organisms is germane to primates," said Weindruch. "We continue to believe that mechanisms that combat aging in caloric restriction will offer a lead into drugs or other treatments to slow the onset of disease and death."

Study details

The research, which commenced in 1989, followed 76 rhesus monkeys, who were fed either a calorie restricted or ad libitum diet from between the ages of seven to 14 years of age.

"We study caloric restriction because it has such a robust effect on aging and the incidence and timing of age related disease," said corresponding author Rozalyn Anderson, who noted that research in flies and other animals has suggested such approaches can extend life by up to 60%.

The effects of caloric restriction on primates are not conclusive, with a 2012 report on 120 monkeys studied at the National Institute of Aging (NIA) showing no differences in survival for caloric restriction animals and a trend toward improved health that did not reach statistical significance.

However the researcher behind the new data suggested that the discrepancy in the NIA data may be a result of how the feeding was implemented in control animals – with suggestions that the control monkeys were actually also calorie-restricted.

"We started with adults,” explained co-author Ricki Colman. “We knew how much food they wanted to eat, and we based our experimental diet on a 30% reduction in calories from that point."

In contrast the NIA monkeys were fed according to a standardised food intake chart designed by the National Academy of Science, she said.

The US-based researchers also noted that they began to see diabetes among the control animals while they were still in the prime of life, within six months after beginning their study.

The contrast with the restricted animals could not have been more dramatic, Colman said: "Until two years ago, we did not have evidence of diabetes in any caloric-restriction animal, but we had a significant numbers of diabetes, or pre-diabetes, metabolic syndrome, in the control animals."